Method and apparatus for pressuring well bores



SePt- 17, 1957 R. c. BAKER EITAIr l 'I 2,806,532

METHOD AND APPARATUS FOR PRESSURING WELL.v BRS Filed Oct. 12, 1953 2 Sheets-Sheet 1 `Admw-/N B. CMQAb, INVENTORS.

rraeA/EYS Sept. 17, 1957 L R. c, BAKER lET AL METHOD AND APPRATUS FOR PRSSURING WELL BORESA Filed Oct' l2, -1953 TTOENEYS United States Patent G METHOD AND APPARATUS FOR PRESSURING WELL BORES Reuben C. Baker, Coalinga, and Martin B. Conrad, Downey, Calif., assignors to Baker Oil Tools, Inc., Los Angeles, Calif., a corporation of California Application October 12, 1953, Serial No. 385,333

14 Claims. (Cl. 166-42) The present invention relates to the application of positive and negative fluid pressures to well bores, and more particularly to localized regions or zones in the well bores.

Heretofore, perforations in casing disposed in a well bore have been `straddled by packing members to provide a localized zone or region between the packing members in which pressure could be applied to the casing, the pressure being imposed through the perforations to the formation in the well bore containing the casing. The packing members, if the tool is of the retrievable type, are secured together in some fashion at a fixed longitudinal distance apart, thereby correspondingly limiting the length of the localized zone to a fixed distance. They are also incapable of withstanding safely relatively high pressures, such as are oftentimes required in the performance of certain operations in the well bore, like formation fracturing, acidizing, cementing and testing.

It is an object of the present invention to provide an improved method and apparatus for straddling casing perforations and for applying high pressures safely to the locations surrounding the casing perforations.

Another object of the invention is to provide a method and apparatus for varying the distance that longitudinally spaced packing members or structures are separated from each other, in order to enable the most -optimum spacing to be selected when the apparatus is disposed in the well casing.

A further object of the invention is to provide upper and lower packing structures in a well casing on opposite sides of casing perforations and selectively set the packing structures at any point in the well casing separated by various distances from each other, then releasing one or both of the structures for resetting at other locations in the well casing, or for complete removal from the well casing. In a more limited sense, the lower packing structure can be set in the well casing to withstand fluid pres- -sures from above or below the structure, or both, which is also true of the upper packing structure.

In its general aspects, the invention includes the securing of an upper retrievable well packer to a tubular string, such as a string of tubing or drill pipe, this upper packer being releasably coupled to a lower retrievable packer or bridge plug. The combination of apparatus is run in the casing to the desired point, as below a series of casing perforations, at which the lower retrievable packer is to be set. This packer is then set in the well casing and the upper retrievable packer released therefrom, whereupon the upper packer can be elevated in the well casing away from the lower packer and set in the casing at any desired point, such asrabove the casing perforations. Pressure can now be applied to iluid in the tubular string, the uid passing out of the upper packer and into `the localized zone between the upper and lowerpackers, the pressure being imposed through the perforations on the formation surrounding the perforated region of the casing. During such imposition of pressure through the tubular string, the lower retrievable packer is set in the well casing, being anchored against downward movement therein and preventing leakage of uid thereby.

lf desired, instead of applying a positive pressure in the well casing between the upper and lower packers, a negative pressure can be applied therein, as, for example, by swabbing the tubular string, whereupon any fluid in the formation will tend to flow through the casing perforations into the localized zone between the packers, and then upwardly into the tubular string. Such application of negative pressure to the localized zone usually results in a greater pressure being present below the lower retrievable packer or bridge plug. Accordingly, this lower packer is preferably of the type that can also be anchored to the well casing against upward displacement, and which will also prevent upward passage of fluid between the lower packer and the well casing. The upper retrievable packer may also be of the type that will prevent fluid in the annulus between the tubular string and the well casing to pass down around the upper packer.

If desired, following the performance of the required pressuring operation at the particular zone in the well casing, the upper packer is released from the well casing and the tubular string lowered to recouple the upper packer to the lower packer, whereupon the lower retrievable packer is released from the well casing and the combination of upper and lower packers then moved either upward or downward in the well casing to a new location at which the lower packer can be reset, the lower packer being released from the upper packer and the upper packer then elevated any desired distance above the lower packer for the purpose of effecting resetting or anchoring of the upper packer against the well casing. Pressure can again be applied through the tubular string to the localized zone between the upper and lower well packers.

The foregoing procedure can be followed as many times as desired in the well casing without removing the packers from the well casing. When the packers are no longer required in the well bore, the upper packer can' be recoupled to the lower packer, both packers being released, whereupon the tubular string can be elevated to remove both packers to the top of the hole and from the well casing.

For any particular setting of the lower packer in the well casing, the upper packer, after having been uncoupled from the lower packer, can be anchored and released as many times as possible without becoming reconnected to the lower packer, the upper packer being settable any number of times and at varying distances from the lower packer. As an example, in the applying of pressure to casing perforations, the lower packer may be set below the perforations, the upper packer uncoupled therefrom and placed a short distance above the lower packer, at which point the upper packer can be anchored in packedoff condition against the well casing. Pressure can then be applied through the tubular string to the localized zone in the casing between the packers, whereupon the upper packer may be released and elevated to a still higher position and the foregoing setting of the packer, pressuring of the localized zone between the packers and release of the upper packer repeated. This vprocedure can be instituted as often as necessary. After all of the perforations have been pressured, in the manner described above, the upper packer can be released in the well casing and lowered for recoupling to the lower packer, whereupon the lower packer is released and all of the apparatus elevated in and from the well casing.

This invention possesses many other advantages and has other objects whichmay be made more clearly apparent from a consideration of a form in which it may be ernbodied. An apparatus for practicing the method is shown in the drawings accompanying and forming part of the present specification. Such apparatus and the method will now be described in detail, for the purpose of illustrating the general principles of the invention. lt is to be understood, however, that such detailed description is not to be taken in a limiting sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings:

Figure 1 is a side elevational view of an apparatus, with the parts in position for the apparatus to be raised or lowered in a well casing disposed in a well bore;

Fig. 2 is a view similar to Fig. l disclosing the lower packer anchored to the well casing below the casing per forations, the upper packer being released from the lower packer and anchored in the well casing above the casing perforations;

Fig. 3 is a fragmentary longitudinal section, on an enlarged scale, disclosing a portion of the lower retrievable packer anchored against downward movement in the well casing;

Figs. 4 and 4a together constitute a longitudinal section through the lower retrievable packer and the device for coupling the upper packer to the lower packer and for retrieving the lower packer, Fig. 4u constituting a lower continuation of Fig. 4;

Fig. 5 is a cross-section taken along the line 5 5 on Fig. 4a.

The apparatus disclosed in the drawings is adapted to be run in a well casing A on the lower portion of a tubular string B, such as a string of drill pipe or tubing. This tubular string is connected to the upper end of an upper retrievable packer C, of any suitable type, this retrievable packer being, in turn, connected to a coupling and retrieving device D releasably connected to a lower retrievable packer or bridge plug E.

The lower retrievable packer or bridge plug E may be of any suitable type capable of being anchored in the well casing A in leakproof relation with respect thereto. The lower retrievable packer is specifically disclosed, described and claimed in our co-pending application for Retrievable Bridge Plug, Serial No. 385,334, filed October 12, 1953, to which attention is invited. The coupling and retrieving device D may be of any suitable type, which is capable of effecting a releasable connection between the upper and lower retrievable packers C, E, in order to enable the packers to be disconnected from one another, `and then reconnected to one another. The coupling device specifically disclosed is more particularly described and claimed in our application for Releasable Apparatus for Retrieving Subsurface Well Devices, Serial No. 385,335, filed October 12, 1953, now Patent No. 2,778,428. The upper retrievable packer is of any suitable type, the one specifically disclosed being described and claimed in the patent to Reuben C. Baker, Patent No. 2,368,400.

The upper retrievable packer, as particularly described in the above-identified Patent No. 2,368,400, includes a central mandrel or body threadedly, or otherwise suitably, secured to the lower end of the tubular string B. Secured to a lower portion of the mandrel or body is a guide 11 on which a generally cylindrical packing sleeve 12 rests, the latter encompassing the body. This packing sleeve engages the lower end of a slip expander 13 that is slidable with'respect to the body, the slip expander' having a plurality of upwardly and inwardly tapering expander surfaces 14 engageable with slips 15 which are coupled together for joint longitudinal movement through a suitable swivel device 16, which is, in turn, connected to a friction drag device 17. In effect, the lower portion of the friction drag device 17 is connected to the slips 15 through the swivel 16 to prevent relative longitudinal movement between the drag device and the slips. The upper portion of the friction drag device is attached to an upper collar 18 slidable on the body or mandrel 10 of the retrievable packer C.

The retrievable packer `also includes a suitable lock device to preclude relative longitudinal movement between the body 10, expander 13 and slips 15. As disclosed, a coupling pin 19 is secured to the body 10, the pin being movable within a J slot 20 in a sleeve 21 forming part of the drag device 17 and slidably mounted on the body 10. When the pin 19 is located in the horizontal or foot portion 22 of the J slot, such as disclosed in Fig. l, the slips 15 and packing sleeve .12 are held in retracted position, since relative longitudinal movement between the packer parts cannot occur. However, when the tubing string B is turned, as to the left, to place the pin 19 in alignment with the longitudinal leg 23 of the slot, then the body 10 of the tool is movable upwardly to shift the expander 13 upwardly within thel slips 15, urging the latter radially outward into anchoring engagement with the well casing A, whereupon a continuation of the upward movement of the packer body moves the guide 11 toward the expander 13 to foreshorten the packing sleeve 12 and expand it into tight sealing engagement with the well casing A. The set condition of the upper well packer C is disclosed in Fig. 2.

When it is desired to retract the upper packer C from the well casing, it is merely necessary to lower the body 10 of the packer, the drag device 17 preventing the slips 15 from moving longitudinally, which allows the guide 11 and expander 13 to be moved in a downward direction, the expander being removed from wedging engagement with the slips 15 to effect inward retraction of the latter from the well casing, the guide 11 moving longitudinally down away from the expander 13 to `allow the packing sleeve 12 to inherently contract to its initial retracted position, such as shown in Fig. l, The tubular string B can then be turned to the right when the parts are in retracted position to move the pin 19 within the foot portion 22 of the J slot 20, which is the locking position. Thereafter, the tubing string B can be elevated in the well casing A without danger of expanding the slips 15 and packing sleeve 12 outwardly against the well casing.

The lower portion of the upper retrievable packer C is connected to the coupling and retrieving device D which is, in turn, releasably coupled to the upper portion of the lower retrievable packer or bridge plug E. This latter apparatus, `as shown in the drawings, includes a central body 25 which may be of several portions, including an upper portion 26, the lower end of which is threaded onto the upper end of a lower body portion 27 A set of upper segmental slips 28 is disposed around the body, these slips having upper head portions 29 whose inner surfaces 3f) are inclined in a downward and inward direction for cooperation with companion tapered surfaces 31 on an upper expander 32 suitably secured to the body 25 of the tool. When the upper expander 32 is moved downward with the body 25 relative to the upper slips 28, the latter are urged in an outward direction to embed their wickers 33 into the wall of the well casing or conduit A, thereby anchoring the body 25 of the tool to the conduit against downward movement.

The upper expander 32 is prevented from moving longitudinally of the body by having its lower smaller end engage a shoulder 34 on the body, with its upper end bearing against a packing cup thimble 35 receiving thc lower or base portion of an upwardly facing packing cup 36, which may be made of rubber or rubber-like material. This cup has an upper lip portion 37 adapted to slidably seal against the wall of th'e well casing, to prevent downward passage of fluid between the packing cup and the casing. The packing member 36 itself is prevented from moving longitudinally with respect to the body by a clamp and valve cage 38, the lower portion of which is threaded onto the upper end of the body 25, bearing against the base of the packing cup 36, the latter, in turn, bearing against the thimble 35, which engages the upper expander 32, whose lower portion, as previously described, engages the body shoulder 34.

A set of lower segmental slips 39 'also encompasses the body 25, these lower slips including lower head portions 40 whose inner surfaces 41 taper in an upward and inward direction for cooperation with a companion tapered surface 42 on a lower expander 43 secured to the body 25 of the tool. The lower expander 43 is prevented from moving longitudinally of the body by the engagement of its upper smaller end :against a 'shoulder 44 provided by the lower end of the upper body portion 26, its lower end engaging a lower thimble 45 surrounding the body and receiving the base portion of a lower packing member 46, which is similar to the upper packing member 36, although reversed in position on the body of the tool. The lower packing 46 faces in a downward direction, its lower lip portion 47 being adapted to slidably seal against the wall of the well casing A to prevent upward passage of lluid between the packing and the well casing. In a manner similar to the upper packing, the lower packing is prevented from moving longitudinally of the body by a lower retainer and valve cage 48 threaded onto the lowermost portion of the lower body member 27 and bearing against the base of the packing 46, clamping the latter against the thimble 45, which, in turn, engages the lower end of the lower expander 43, which is prevented from moving upwardly by the body shoulder 44.

When the body of the tool and the lower expander 43 move upwardly with respect to the lower set of slips 397 the lower expander shifts the lower slips laterally outward, to embed their wickers 49 into anchoring engagement with the well casing, thereby preventing the tool from being moved upwardly within the Well casing. The lower packing 46 prevents lluid from passing in an upward direction between the body 25 of the tool and the well casing.

Relative longitudinal movement between the body 25 and the expanders 32, 43 mounted thereon, on the one hand, and the sets of upper and lower slips- 28, 39, on the other hand, is secured by resisting the longitudinal movement of the slips through the medium of a drag device. The drag device disclosedin the drawings includes longitudinally extending drag blocks 50 circumferentially spaced from one another 'and slidably mounted in longitudinal grooves 51 in a slip and drag block housing 52 slidable along the exterior of the tool body. The drag blocks 50 are urged outwardly into frictional engagement with the wall of the Well casing by a plurality of helical compression springs 50a bearing against the bases of the confining housing grooves 51. Outward movement of the drag blocks 50 is limited 1oy their engagement with upper and lower stop rings 5012 secured to the housing injany suitable manner.

Both the upper yand lower sets of slips 38, 39 are secured to the housing 52, in order that the'drag blocks 50 will resist movement of the slips within the well casing, and enable the body 25 and the upper and lower expanders 32, 43 to be shifted longitudinally with respect thereto. Thus, the upper slips 23 have depending arms 53 terminating in inwardly directed llanges 54 received within a circumferential groove 55 provided in the mid-portion of the housing 52 between the circumferentially spaced drag blocks 50. Each slip segment `structure i's longitudinally slotted throughout substantially their entire length to a region adjacent the flange 54, enabling the arms 53 to llex and allowing the slips to be deected in an outward direction into engagement with the well casing Wall. The flange portions 54 of the slips themselves are prevented from coming out of their companion grooves by an arcuate holding device 57 disposed across the flange portion and 6 secured to the slip and drag block housing 52 by one or more screws 58.

The lower set of slips 39 is attached to the housing 50 in the same manner as the upper set of slips 28, this lower set of slips having upper inwardly directed flanges 54 received within arcuately spaced grooves 55 in the housing 52 between the drag blocks 50 and retained therein by the same slip holder 57 that maintains the upper slip anges 54 in their grooves. The lower slips 39 are also longitudinally slotted from a region adjacent their llange portions 54 to the lower ends of the slips to provide flexible or spring-like arms 53a that will enable the head portions 40 of the slips 39 to be expanded laterally outward into anchoring engagement with the well casing A.

The drag block stop rings 50h are spaced laterally outward away from the slip arms 53, 53a a suicient distance to allow the heads 29, 40 of the slips 2S, 39 t-o move without restraint laterally into engagement with the well casing. The slips themselves normally tend to remain in an inward direction because of the spring characteristics of their arm portions 53, 53a. However, assurance is had that the slips are held in a retracted position when they are not to be expanded Ioutwardly into engagement with the well casing by slip retainer and retractor rings 60, 61 engageable with the upper and lower sets of slips 28, 39. Thus, an upper ring 60 is disposed around the shoulder portions 62 of the upper set of slips 28, which interconnect the head and arm portions 29, 53, the shoulder portions being thicker in radial dimension than the arm portions, their outer surfaces being 'adapted to engage the ring 60, which will prevent the wickers 33 of the slip heads from rniving into engagement with the casing wall. The shoulder portions 62 are interconnected with the arm portions 53 by the tapered surfaces 63, which are capable of engaging the upper end of the ring 60, in order to urge the slip heads 29 in an inward direction.

The retainer and retractor ring 60 is supported in position by a plurality of longitudinally extending bars 64 disposed hetween the slip segment 28, their lower ends being welded to the upper end of the ring 60 and their upper portions being clamped between the upper expander 32 and upper thimble 35, the upper portions of the bars being prevented from disconnecting from the upper expander by a holding ring 65 encompassing the bars and suitably secured to the expander.

The lower set of slips 39 is similarly held in retracted position against inadvertent outward movement by the lower retainer and retractor ring 61 encompassing the enlarged shoulder portions 67 of the lower slips, the lower end of this ring being engageable with the tapered surfaces 68 on the slip segments which interconnect the shoulders 67 and the arm portions 53a, to urge the lower slip heads 40 inwardly away from engagement with the casing. The lower ring 61 is held in appropriate position by a plurality of circumferentially spaced and longitudinally extending bars 69 welded to the lower end of the ring 61, the bars being clamped between the lower expander 43 and the lower thimble 45, and held in appropriate posittion on the lower expander by an encompassing holding ring 70 suitably secured to the lower expander. As is true of the upper slips 28, the lower stop ring 50b is spaced suiciently away from the lower slip arms 53a to avoid interference with the laterally outward movement of the lower slips 39 into engagement with the well casing.

Since the drag blocks 50 are resisting longitudinal movement Iof the upper and lower sets of slips 28, 39 in the well casing, relative longitudinal movement of the body 25 and the upper and lower expanders 32, 43 connected thereto will expand either the upper or the lower slips into anchoring engagement with the wall of the well casing, depending upon the direction of longitudinal movement of the body 25 and the expanders 32, 43. Thus, should the body and exp-anders be moved downwardly, then the upper expander 32 will be moved down within .the upper slips 28, shifting the latter radially outward into anchoring engagement with the well casing, these slips,

in effect, bending or rocking about their lower flange portion 5,4. It is to be noted that when the upper slip heads 29 arein theirvretracted position, the tapered slip surfaces 30 are not parallel to the expander surface 3l, but make an acute angle therewith. The difference in inclination is provided so that when the slips 28 are rocked outwardly into engagement with the well casing the surfaces 30, 31 are substantially parallel, the expander surface 3l making full bearing contact against the slip surfaces 33.

The relative downward movement of the body 25 and expanders 32, 43 with respect to the slips will anchor the upper slips 28 against the well casing. However, the lower slips 39 will still remain in a retracted position, since the lower expander 43 is moving downward away from them. On the other hand, should the body 25 be moved in an upward direction, then the body and expanders 32, 43 will be shifted upwardly with respect to the slips, the upper expander 32 moving out of wedging engagement within the upper slips 23, this upward movement causing the retainer' and retractor ring oil to engage the tapered slip surfaces 63, to insure the inward movement of the slip heads 29 out of engagement with the well easing, the ring 6i) moving at least slightly over the shoulder portions 62 to retain the slips 28 in this retracted position.

Upward movement of the lower expander 43 will move the lower retainer and retractor ring ol out of a position to engage the lower slip shoulders 67, whereupon the lower expander 43 can be wedged upwardly within the lower slips 39 to urge the latter radially outward into engagement with the wall of the well casing. As is true of the upper expander 32 and upper slips 28, the tapered surfaces 42, 41 on the lower expander 43 and lower slips 39 are not parallel to one another when the lower slips are in retracted position, the surfaces making `an acute angle with respect to each other. However, when the lower expander 43 moves upwardly within the lower slips 39, the latter are rocked or pivoted about their flange portions 54 outwardly against the casing, in which position their tapered surfaces 4l will be substantially parallel to the lower expander tapered surface 42 to insure full bearing engagement lbetween the expander 43 and slips 39.

The ability of either the upper or the lower sets of slips to be moved in a lateral outward direction depends upon the relative longitudinal movement of the body and expanders with respect to the slips. Such relative longitudinal movement is prevented until it is desired to secure an anchoring of the lower retrievable well packer or bridge plug E in the well casing. As disclosed in the drawings, the slip and drag block housing 52 is provided with a pair of diametrically opposed longitudinal slots 73 in its inner wall in which the outer ends of the at crosspiece or oai` 74 are received, such outer ends of this bar being adapted to bear against the lower ends 73a of the slots or the upper ends 73b of the slots. This cross-piece 74 extends through diametrically opposite longitudinal slots 75 in the body in alignment with the housing slots 73.

The cross-piece 74 also extends through a transverse slot 76 in a control rod 77 extending completely through the packer body 25. This control rod has an upper reduced diameter portion 78 slidable thro-ugh the transverse portion 79 of the upper valve cage 38. It also has a lower reduced diameter portion 86 slidable through the lower transverse portion 3l of the lower valve cage 48. Thus, the valve cages 38, 48 retain the control rod 77 coaxial of the body 25 of the tool, while permitting the rod 77 to slide longitudinally in an upward or downward direction relative to the tool body 2S. The main intermediate portion of the control rod 77, through which the ,cross-piece 74 extends, has a diameter substantially less than the inside diameter of the body 2S, to afford ample passage area for the ilow of fluid through the body.

When the control rod 77 is shifted downwardly with respect to the body, the cross-piece 74 will engage the lower ends 73aof the housing slots 73 and will shift the housing 52 in a downward direction along the body 25 a comparatively short distance until the cross-piece engages the lowerV ends 75a of the body slot 75. The distance that the slip and drag block housing 52 is thus moved is comparatively short, the parts being so proportioned that the drag block housing 52 and the slips 28, 39connected thereto are disposed in substantially a central position between the upper and lower expanders 32, 43. When the cross-piece 74 engages the lower ends 75a, 73a of the body slots 75 and housing slots 73, downward movement of the control rod 77 will carry the body 25 and the drag block housing 52 downwardly as a unit7 permitting no relative downward movement of the upper and lower expanders 32, 43 with respect to the upper and lower slips 28, 39, the `slips remaining in their neutral retracted positions, such as disclosed in Fig. 4a. Similarly, in the event the control rod 77 is moved upwardly within the housing, the upper end of the cross-piece 74 will engage the upper ends 75b, 73h of the body slots 75 and the housing slots 73, further upward movement of the control rod then carrying the body 25 and housing 52 upwardly as a unit with it, the body being prevented from moving upwardly relative to the housing 52, and thereby preventing relative upward movement of the expanders 32, 43 with respect to the slips 28, 39, which causes the slips to remain in their neutral unexpanded position.

The placing of the cross-piece 74 in an intermediate position within the housing and body slots 73, 75 allows the body 25 and the upper and lower expanders 32, 43 connected thereto to move in lboth an upward and a downward direction a suicient distance to either wedge the upper expander 32 into the upper slips 28, in the event downward movement of theVv body 25 and exp-anders 32, 43' occurs, or to wedge the lower expander 43 into the lower slips 39, in the event that upward movement of the body 25 and Iexpanders 32, 43 occurs. When relative downward movement of the body 25 and its expanders occurs, the yupper slips 28 are embedded in the well casing, to prevent downward movement of the lower packer E, and, conversely, when upward movement of the body and expanders occurs, the lower expander 43 is embedded into the lower slips 39, to wedge them into anchoring engagement with the well casing and prevent upward movement lof the well packer -in the well casing A.

When there are no upward or downward directed forces imposedl on the control rod 77 tending to shift its crosspiece 74 either downwardly within the body and housing slots 75, 73, or upwardly therewithin, the control rod and its cross-piece are disposed inl a central neutral position with respect to the slots, such as disclosed in Fig. 3. This central disposition is provided by upper and lower springs 85, 86, which fare availed of to locate the control rod 77 in a central or neutral position, and also to determine the open or closed position of the passage 87 through the packer or bridge plug body 25.

The upper helical compression spring is disposed on the upper reduced diameter portion 78 of the control rod, this spring engaging the upper valve cage 38 and also an upper valve head 88 slidable in a downward direction along the reduced diameter portion 78 of the control rod into engagement with the valve seat 89 provided within the upper portion of the tool body 25. The spring 85 tends to urge the valve head 88 downwardly, so that its cylindrical portion 88a is disposed within the upper valve seat 89, as determined by engagement of the valve head stop ange 90 with the upper end 91 of the'body 25. The valve head 88 is provided with a suitable rubber or rubberlike side seal ring 92 adapted to engage the cylindrical valve seat portion 89 of the body. Leakage of fluid between the control rod 78 and valve head 88 is prevented by a rod packing ring 94 engaging the periphery of the rod 78.

A lower valve device is also provided, including a lower valve head 96 urged in an upward directionv into sealing engagement with acylindrical valve seat 97 provided at the lower end of the packer body 25. The helical compression spring 86 surrounds the lower reduced diameter portion 80 of the control rod,its lower end bearing against the valve cage 48 and its upper end against the valve head 96, urging the latter in an upward direction to shift it within the lower cylindrical valve seat 97, as determined by engagement of a ange 98 on the valve head with the lower end 99 of the body 25. Leakage of iluid between the head 96 and the cylindrical valve seat 97 is prevented by a side seal ring 100 mounted in the valve head 96 and adapted to sealingly engage the valve seat 97. Leakage of uid between the lower reduced diameter rod portion 80 and the lower valve head 96 is prevented byV a rod packing ring 102 in the valve head 96 slidably and sealingly engaging the control rod portion 80.

The upper spring 85 not only urges the upper valve head downwardly into sealing engagement with the upper valve seat 89, but also engages the upper valve head 88 with an upper shoulder 104 formed on the control rod 77 to shift the control rod in a downward direction. Similarly, the lower spring 86 urges the lower valve head 96 in an upward direction toward a position of engagement with its valve seat 97, this lower valve head being engageable with a lower downwardly directed shoulder 105 on the rod and tending to elevate the rod 77 within the packer body 25.*. When the rod 77 is unrestrained by external forces, the springs 85, 86 shift the valve heads into engagement with their seats, the heads 88, 96 engaging the rod shoulders 104, 105 and disposing the rod in a central position in which the cross-piece 74 is located approximately midway within the body and housing slots 75, 73 (such as shown in Fig. 3), to allow the body 25 and expanders 32, 43 t0 be shifted relative to the slips 28, 39 for the purpose of urging either the upper or the lower slips outwardly into engagement with the well casing.

The springs 85, 86 and valve heads 88, 96 are effective to center the control rod 77, in the manner described above, through engagement with the rod shoulders 104, 105. Conversely, the rod shoulders 104,105 are effective to engage the valve heads 88, 96 and hold them in open poistions. Thus, a downward force imposed on the control rod 77 will cause the lower shoulder 105: to engage the lower head 96 and shift it oi its seat 97 to open position. Similarly, upward movement of the control rod 77 will shift the upper shoulder 104 into engagement with the upper valve head 88 to move it out of engagement from its companion seat 89 against the force of the upper spring 85.

The springs 85, 86 are effective to place the control rod 77 in a central position, as described above. They are also cooperable with their respective valve heads S8, 96 to shift the latter to valve closing position. In effect, the valve heads 88, 96 and springs 85, 86 constitute oneway or check valves, the fluid pressure within the tool being effective to shift the valve heads 88, 96 to-open positions against the force of the springs 85, 86 during the actual elevating or lowering of the tool inthe well casing, or the fluid pressure is effective to act on the heads 88, 96 to shift them to closed position, supplementing the force of the springs.

The lower retrievable plug or packer E, as stated above, is releasably coupled to the upper retrievable Packer C by means of a suitable coupling and retrieving device D, which is disclosed in the drawings as being a form of overshot. lt includes an outer housing or cylinder 120 threaded onto a sub 121 which is, in turn, threaded into a collar 122 threadedly secured to the tubing member 122av depending from the body portion 10 of the upper retrievable well packer C. The cylinder 120 has a depending wash-over sleeve 123 secured to it to facilitate the location of the overshot or retrieving apparatus centrally with respect to the bridge plug E. The lower 10 portion of the wash-over sleeve 123 can encompass the upper valve cage 38 and will tend to centralize the housing or cylinder with respect to the control rod 77, to which the retrieving and running-in device D is actually tobe associated.

The control rod 77 extends upwardly to a substantial extent above the upper valve cage 38 and is provided with an upper head 124 extending outwardly from the reduced diameter portion 78 of the control head to form an outwardly directed shoulder 125 adapted to be engaged by the inward nose portions 126 of latch members 127 that are carried by an annular piston 128 slidable in the cylinder 120, and also along an inner cylinder member o-r mandrel 129 threaded into the lower end of `the tubular sub 121. The inner and outer cylinder members 129, 120 actually define an `annular cylinder space 1'30 within the housing 120 containing the annular piston 128. Leakage along the inner and outer walls of the annular piston 128 is prevented by suitable side seal rings 131 mounted in the inner and outer walls of the piston and slidably engaging the walls of the inner and outer cylinder members 129, 120. The upper portion of the piston 128 is enlarged to provide a stop shoulder 132 engageable with a companion stop shoulder 133 on the mandrel. v

The piston is normally urged in a downward direction by a helical compression spring 134 encompassing the mandrel 129, its lower portion engaging the Piston 128 and its upper portion the lower end of the sub 121. Any uid that might be disposed in the annular cylinder above the piston rings 131 may be dispelled from the cylinder through one or more bleeder ports 135 provided through the upper portion of the outer cylinder 120 and communicating with the annular cylinder space 130.

The latches of dogs 127 are pivoted to the lower portion of the piston 128, as by providing outwardly extending hooks 136 on the latches received within an annular groove 137 in the lower portion of the piston. These dogs' 127 extend downwardly from the piston along the lower portion of the mandrel, the mandrel having a tapered nose 138 engageable with the upper surfaces 139 of the latch noses 126 and tending to urge the latches 127 in an outward direction. The lower ends 140 of the latches are engageable with a downwardly and inwardly inclined surface 141 in the lower portion of the cylinder or housing 120, which tends to urge the noses 126 of the latches under the control rod shoulder 125. When the latches are disposed in a still lower position with respect to the outer cylinder member 120, their outer surfaces 142 are engageable with the downward and inwardly tapered surface 143 disposed below the surface 141 iust mentioned, which securely hold the latches 127 under the control rod shoulder 125.

The wash-over apparatus D is not -only used for retrieving the lower retrievable packer E from the well casing A, but it is also useful in moving the plug E down the casing in the rst instance. To accomplish this purpose, a spider 144 is secured to the upper portion of the control rod 77 below its latching shoulder 125. This spider includes an outer ribbed portion 145 adapted to engage a downwardly flaring inner surface 146 on the lower end of the cylinder 120. The ribbed portion 145 is secured to a sleeve 147, which rests upon a split snap ring 148 contained within a peripheral groove 149 in the control rod 77, in order to prevent downward movement of the spider 144 and its sleeve along the control rod. The upper end 150 of the sleeve 147 is tapered in an upwardand inward direction and is spaced a sufficient distance below the rod shoulder 125 to allow the latch noses 126 to move inwardly into complete engagement with the rod shoulder 125.

ADuring downward movement of the apparatus in the well casing, the lower aring surface 146 of the outer cylinder 120 is engaging the spider 144, the downward motion of the tubing 122a, collar 122, sub 121 and cylinder 126 being transmitted through the spider to the control rod 77, whereby the latter is shifted to its lowermost Vposition within the. body 25, the lower rod shoulder 165 holding the valve 96 open, and the cross-piece 74 being disposed at the lower ends of the housing and body slots 73, 75, precluding setting of the plug E in the casing A. During such lowering movement, it is immaterial whether or not the latches 127 are coupled to the control rod 77 by being engaged under the rod shoulder 125, since the downward movement can be transmitted between the overshot housing 120 and the control rod 77. As disclosed in Fig. 4, the latches 127 arein a position to engage the periphery of the spider sleeve 147 and will not engage the shoulder. rlChe spring 134 is urging the piston 128 in a downward direction, but the piston cannot move downwardly since the latch noses 126 engage the spider sleeve 147.

When it is desired to rem-ove the overshot or retrieving tool D from the plug E, to allow the latter to anchor itself in the well casing A, the tubing string B and upper well packer C need merely be elevated, which will elevate the housing 12 with respect to the control rod 77, thereby removing the downward force on the control rod and allowing it to assume its neutral position, such as disclosed in Fig, 3. Should the force of the spring 134 be suficient to shift the latch noses 126 under the shoulder 125, upon upward movement of the cylinder 120 and mandrel 129, release can be effected simply by applying pressure to the uid in the tubular string B, this pressure passing downwardly through the sub 121 and the mandrel 129, being throttle because of the narrow space or annular orifice provided between the spider sleeve 147 and the narrow portion of the passage through the cylinder 120,

Such throttling action builds up suiicient back pressure under the piston 128 to shift it in an upward direction against the force of the spring 134, carrying the latches 127 upwardly and causing the latch noses 126 to engage the lower end 138 of the inner cylinder member or mandrel 129, which shifts them laterally outward to a position in which the noses are incapable of engaging the control rod shoulder 125. The tubing string B may now be elevated to completely remove the retrieving device or overshot D from the control rod 77 thereby disconnecting the upper packer C from the lower packer E, the entire tubing string retrieving device D and upper packer C being movable upwardly in the well casing A.

v lf it is desired to recouple the overshot D to the control rod 77, the tubular string B, upper packer C and overshot D are lowered, the. noses 126 of the latches 127 engaging the upper tapered head 124 of the control rod, which will shift the latches 127 outwardly and the piston 12S upwardly against the spring 134, until the latch noses 126 are disposed lower than the shoulder 125, whereupon the spring 134 is effective to shift the latches downwardly along the outer cylinder tapered surface 141, which will urge the latch noses 126 under the control rod shoulder' 125. Further downward movement of the latches will engage their outer surfaces 142 with the holding surface 143 of the outer cylinder member 120, which will posi tively preclude outward movement of the latches 127 from their coupling position under the control rod shoulder 125. An upward elevation of the tubular string B, retrievable packer C and the overshot D will then cause the holding surface 33 to urge the latches 127 more firmly into engagement with the shoulder 125 of the control rod 77, causing the latter to move upwardly, shifting the cross-piece 74 into engagement with the upper ends of the housing and body slots 73, 75, thereby locating the slips 2S, 39 in their central and neutral position relative to the expanders 32, 43 and body 25, and preventing relative upward longitudinal movement between these parts. Accordingly, the entire apparatus disclosed in the drawings can be elevated in the well casing. Similarly, if thertubular string B, upper packer C and overshot D are moved in a downward direction, the control rod 77 is shifted toits lowermost position within the packer body to locate the cross-piece 74 in engagement with the lower ends of the housing and body slots 73, 75. Here again, the slips 28, 39 are held in a neutral position with respect to the expanderrs 32, 43, in order that downward movement of the control rod 77, body 25, expanders 32, 43 and slips 28, 39 will occur as a unit, to preclude expansion of the slips against the casing A.

The apparatus is made up at the top lof the well bore, with the parts occupying the relative positions disclosed in Fig. l and Figs. 4 and 4a, the upper retrievable packer C having its slips 15 and packing sleeve 12 in retracted position, with its J slot pin 19 located in the horizontal portion 22 of the slot Ztl. The overshot D is disposed over the control rod 77, with the lower flaring end 146 of the outer cylinder member engaging the spider 144, The combination of apparatus is inserted in the well casing and lowered therewithin, the downward motion onvthe tubing string B and upper retrievable packer C being transmitted through the overshot D to the control rod 77, shifting the latter downwardly of the body 25 of the lower retrievable packer E, locating the cross-piece 74 in engagement with the lower ends of the housing and body slots 73, 75, which hold the slips 28, 39 in their neutral position and causing the lower control rod shoulder 105 to engage the lower valve member 96 and hold it downwardly in open position from its seat 97 against the force of the helical spring 86.

The apparatus can be lowered in the well casing until the point is reached at which it is desired to set the lower retrievable packer E. As an example, if it is desired to set the packer immediately below casing perforations P, then the apparatus is lowered until the lower packer E is located at such position. During such lowering movement of the apparatus, the uid in the well casing A can by-pass the lower retrievable packer E by owing through the openings in the lower valve cage 48 and through the open lower valve seat 97 into the body 25, the fluid forcing the upper valve head 88 from its seat 89 against the force of the spring 85 and passing out through the openings in the upper valve cage 38 and into the Well casing thereabove. This uid can flow around the wash-over sleeve 123 into the annulus between the tubing 122a and the casing A, passing upwardly along the exterior of the upper retrievable packer C and up along the exterior "of the tubing string B thereabove. Some of the yfluid canalso pass up through the spider 144 and into the inner cylindrical member 129, continuing on through the sub 121 and tubular extension 122s, through the tubular body 1) of the upper retrievable packer C and into the tubular string B, for the purpose of automatically filling the latter with the fluid in the well casing.

When the location in the well Icasing is reached'at which the lower retrievable packer is to be set, as below the casing perforations P, it is merely necessary to apply pressure to the fluid in the tubular string B, the uid under pressure being restricted by the orice or passage formed between the spider 144 and the outer cylindrical member 120, which builds up a back pressure capable of acting on the lower surface of the annular piston 128, moving the latter in an upward direction against the force of its spring 134, which shifts the latches 127 upwardly and, through engagement with the lower tapered nose 138 of the inner cylindrical member 129, expands the latches 127 in an outward direction, whereby they are incapable of engaging the latching or locking shoulder on the upper end of the rod 77. The tubing string B may Inow be elevated, to remove the overshot D from association with the control rod 77 and the spider 144, the tubing string B being moved upwardly to as great aV distance as desired. As an example, the tubing string may 'belelevated until the retrievable packer C is located just above the casing perforations P.

When the overshot D is removed from the control rod 77, the springs 85, 86 are effective to shift the control rod to a central position, which is accompanied by the centering of the cross-piece 74 in the housing and body slots 73, 75. The friction of the packing cups 36, 46 against the casing A will tend to hold the lower packer E in the position to which it has been run in the well casing, but, should there be a predominance of pressure either above or below the lower retrievable packer E, then such pressure will act on either the upper or the lower valve 88 or 96 to close the body passage 87. It will also act on either of the packing cups 36 or 46 to shift the body 25 and expanders 32, 43 in a particular direction to expand one set of slips outwardly into anchoring engagement with the well casing. Should there be a pressure diiferential below the packer E, it will shift the lower valve 96 into engagement with the lower seat 97 to close the body passage, whereupon the pressure will act on the body 25 of the tool and the lower packing cup 46 to shift the body 25 and the expanders 32, 43 in an upward direction, to wedge the lower expander 43 into the lower slips 39 and expand the latter outwardly against the well casing A. A pressure differential above the packer E will close the upper valve 8S, 89, shifting the upper packing 36 downward, as well as the body 25 and expanders 32, 43, to wedge the upper expander into the upper slips 28.

The foregoing relative movement between the body 25 and expanders 32, 43, on the one hand, and the slips 28, 39, on the other hand, can take place, since the longitudinal movement of the slips is resisted by the friction drag blocks 50, the cross-piece 74 being in a central position within the slots 73, 75, so as to avoid interference with such relative longitudinal movement.

The upper retrievable packer C can now be anchored to the Well Icasing above the perforations P, as by turning the tubing string B to the left, for example, to place the pin 19 in alignment with the longitudinal leg 23 of the slot 20, the friction drag springs 17 resisting longitudinal movement of the slips 15 and allowing the tubing string B and body 10 to move upwardly for the purpose of causing the expander 13 to move upwardly Within the slips 15 and expand the latter radially outward into anchoring engagement with the well casing A, then foreshortening and expanding the packing sleeve 12 into sealing engagement with the well casing A.

Fluid under pressure may now be imposed on the liuid in the tubular string B, this uid passing out through the lower end of the overshot D into the localized casing zone between the upper and lower packers C, E, the fluid passing out through the casing perforations P and into the formation surrounding the perforations. The downward pressure in the localized zone shifts and maintains the upper valve head 88 in closed engagement with its companion valve seat 89, the pressure then acting across the upper body area 2S and the upper packing 36, urging the upper body 2S in a downward direction to wedge the upper expander 32 into the slips 28, anchoring the latter against the casing. Thus, the lower packer E is prevented from moving downwardly in the well casing, its packing cup 36 and closed valve S8, 89 at the upper portion preventing iluid from leaking past the lower packer E. The upper retrievable packer C prevents fluid from passing from the localized zone upwardly therebeyond.

Pressures of a comparatively high order can be imposed on the iiuid in the tubing string B, localized zone, perforations P andV the formation opposite the perforations, the lower packer E being capable of withstanding exceedingly high pressures, which yis also true of the upper packer C.

If desired, the iud level in the tubing string B can be lowered by a swabbing operation, the packing sleeve 12 of the upper retrievable Well packer C being held against the casing A in sealing engagement therewith by the upward strain taken on the tubing string, so as to prevent the hydrostatic head of uid in the tubing-casing annulus above the upper packerl C from being imposed on the localized zone. In eifect, the fluid in the formation may be caused Ito ow through the perforations P into the localized zone and into the tubing B by the swabbing action. If this occurs, the lower packer E will still remain .at its desired position in the well casing, since a predominance of pressure in the localized zone over that in the casing below the lower packer E will hold the latter anchored-to the well casing against downward movement. 0n the other hand, should the pressure in the localized zone become less than that in the well casing below the lower packer, then the fluid pressure from below will close and hold the lower valve 96 in closed position against the body 25, such pressure acting on the body 25 and the lower cup packing 46 to urge the body 25 in an upward direction relative to the slips 28, 39, which do not move longitudinally because of the resistance oiered by the friction drag blocks 50 against the wall of the well casing, thereby causing the lower expander 43 to wedge upwardly within the slips 39 and expand the latter outwardly into firm sealing engagement with the wall of the Well casing.

Accordingly, it is evident that despite the presence of a `greater pressure in the localized zone than below the lower packer E, or a lesser pressure in the localized zone than below the packer, the lower packer E still remains anchored to the well casing at the desired location. Following completion of the operation through the perforations P, the tubing string B may be lowered, to effect retraction of the slips 15 and packing sleeve 12 of the upper packer C, whereupon the tubing string B may be rotated to place the pin 19 in the foot portion 22 of the J slot 20, to lock the upper packer C with its parts in retracted position. The tubing string may now be lowered, to relocate the overshot D over the tapered head 124 of the control rod 77, the head urging the 'lat-ches 127 in an outward direction `against the force of the piston spring 134 until the latches are disposed below the control rod shoulder 125, whereupon the spring 134 is effective to shift they piston 128 downwardly to force the latches 127 under the shoulder 125, in view of the downward movement of the latches along the retracting surfaces 141, 143 of the outer 'cylinder member 120. When the latches 127 are disposed under the shoulder 125, then an upward strain taken on the tubular string will move the holding surfaces 143 of the outer cylinder member 120 behind the latches and hold them locked under the shoulder.

The tubing string B can now be elevated, to correspondingly elevate the upper retrievable packer C, which is now recoupled to the lower retrievable packer E, this upward movement shifting the control rod 77 upwardly with respect to the body 25 of the lower packer until the cross-piece 74 is again disposed in engagement with the upper ends of the body and housing slots 75, 73, which positions the slips 28, 39 in a neutral location relative to the upper and lower exp-anders 32, 43 and precludes relative upward longitudinal movement between the various parts of the lower packer. The tubing string B may now be further elevated, the upper retrievable packer parts C remaining in their retracted position during `such elevating movement, which is also true of the lower packer E. The lower packer, of course, is moved upwardly with the tubing string B, the control rod shoulder 104 having previously engaged the upper valve head S8 to shift it and hold it in an open position, thereby allowing the uid in the well casing to pass down through the body passage 87, unseating the lower valve head 96 and passing outwardly through the lower valve cage 48 into `the Icasing below the lower packer E.

The tubing 'string B may now be elevated in the well casing to completely remove the Iapparatus from the well casing, or it may be elevated to place the lower packer E in another posi-tion in the well casing at which it is to be set. Whenthis position is reached, all that need be done isv to apply pressure to the fluid inthe tubular string, this pressure acting' on the underside of the piston 128 tourge it and the latches 127 in an upward direction, causing the. latches to be released from the control rod shoulder'125 and allowing the tubular string B, upperretrievable packer C and overshot D to be elevated away from the lower packer. The upper packer C may be disposed at the desired new location in the well casing A, whereupon it can be set and pressure again' imposed in the tubular string B and into the localized zone in the casing between the upper and lower packers C, E. Following the completion of the operation in the well casing, the tubular string B may again be lowered, to retract rtheV slips 15 and packing sleeve i2 of the upper packer C, and lock the parts in their appropriate position. The tubular string B, upper packer C and overshot D are then relowered and a-gain recoupled to the control rod 77 of the lower packer, whereupon the parts can lagain be elevated, the elevating movement on the control rod 77 again locating the slips 28, 39 ofthe lower packer in a neutral position, preventing their expansion, which allows the lower packer E to be elevated in the-well casing.

If desired, the combination can be lowered in the well casing instead of being elevated therewithin, to locate the lower packer E at any desired point in the casing, whereupon the overshot D can again be released therefrom, to allow the lower packer to be set and the upper packer C shifted to an appropriate location above the lower packer, afterwhich the upper packer can be anchored in packedolf condition in the well casing and another operation performed in the well bore.

It is evident that following the release of the upper packer C from the lower packer E, it can be moved Iany desired distance above the lower packer E and anchored in packed-off condition within the well casing. It can be anchored in packed-off condition at one point in the .well casing and then it can be shifted to another point and reset in the well casing without becoming recoupled to the lower packer. After each setting, a pressuring operation can be performed, the lower packer E in each instance preventing fluid from passing down the well casing beyond its setting point, as well as preventing fluid from passing upwardly in the well casing past the lower well packer.

After all of the operations have occurred in the well casing, the upper packer C `can be recoupled to the lower packer E and all of the apparatus elevated to the top 'of the well hole for removal. i

It is evident that the combination of packers provides a straddling apparatus that can be run simultaneously in the well casing and set therein at any desired separated points, the distance between the packers being varied to suit conditions. At any time, the upper and lower packers can be recoupled to one another and then later disconnected from one another, the entire arrangement affording great flexibility in performance of operations in the well casing.

A :The inventors claim:

l. The method of applying fluid pressure to a formation zone in a well bore, which comprises simultaneously lowering upper and lower well packers on a tubular string in the well bore to a desired location therein, setting the lower packer in the well bore against downward movement therein and to prevent downward passage of fluid therethrough, elevating the upper packer from the lower packer, setting the upper packer in the well bore, applying fluid pressure through the tubular string and upper packer to the zone in the well bore between the set upper and lower packers, thereafter releasing the upper packer and lowering it toward the lower packer, then connectingthe upper packer to the lowe'r packer, releasing the lower packer, and moving lthe upper and lower packers longitudinally in the well bore.

2. The method of applying uid pressure to formation zones in a well bore, which comprises simultaneously lowering upper and lower well packers on a tubular string in the well bore to a desired location therein, setting the lower packer in the well bore against downward movement therein and to prevent downward passage of iluid therethrough, elevating the upper packer from the lower packer, setting the upper packer in the well bore, applying fluid pressure through the tubular string and upper packer to the Zone in the well bore between the set upper and lower packers, therafter releasing the upper packer and lowering it toward the lower packer, then connecting the upper packer to the lower packer, releasing the lower packer, moving the upper and lower packers longitudinally in the well bore to another location therein, resetting the lower packer in the well bore against downward movement therein and to prevent downward passage of fluid therethrough, elevating the upper packer from the lower packer, setting the upper packer in the well bore, applying fluid pressure through the tubular string and upper packer to the zone in the well bore at said another location between the set packers, thereafter releasing the upper packer and lowering it toward the lower packer, then reconnecting the upper packed to the lower packer, releasing the lower packer, and simultaneously moving the upper and lower packers longitudinally in the well bore.

3. The method of applying lluid pressure to a formation zone in a well bore through a lateral opening in a well casing disposed in the well bore, which comprises lowering upper and lower well packers on a tubular string in the well casing to the region of the casing opening, settingrthe lower packer in the casing below the opening, against downward movement therein and to prevent downward passage of fluid therethrough, elevating the upper packer from the lower packer, ysetting the upper packer in the well casing above the opening, applying fluid pressure through the tubular string and upper packer to the well casing between the set upper and lower packers, thereafter releasing the upper packer and lowering it toward the lower packer, then connecting the upperpaclier to the lower packer, releasing the lower packer, and moving theupper and lower packers longitudinally in the well casing.

4. The `method of applying fluid pressure to a formation zone in a well bore through a lateral opening in a well casing disposed in the well bore, which comprises lowering upper and lower well packers on a tubular string in the well casing to the region of the casing opening, anchoring the lower packer in packed-off condition in the casing below the opening against downward movement therein and to prevent downward passage of tluid therethrough, elevating the upper packer from the lower packer, anchoring theupper packer in packed-olf condition in the casing above the opening, applying fluid pressure through the tubular stringand upper packer to the well casing between the anchored packers, kthereafter releasing the upper packer from the casing and lowering it toward the lower packer, then connecting the upper packer to the lower packer, releasing -the lower packer from the casing, and moving the upper and lower packers as a unit longitudinally in the well casing.

5. The method of applying lluid pressure to a formation zone in a well bore through a lateral opening in a well casing disposed in the well bore, which comprises lowering upper and lower well packers on a tubular string in the well casing to the region of the casing opening, anchoring the lower packer in packed-off` condition in the casing below the opening against downward ymovement therein and to prevent downward passage of fluid therethrough, elevating the upper packer from the lower packer, anchoring the upper packer in packed-off condition in the casing above the opening, applying fluid pressure through the tubular string and upper packer to the well casing between the anchored packers, thereafter releasing the upper packer from the casing and lowering 7 5 it toward the lower packer, then connecting the upper packer to the lower packer, releasing the lower packer from the casing, and elevating the upper and lower packers as a unit in the well casing. p

6. The method of applying iluid pressure to a formation zone in a well bore through a lateral opening in a well casing disposed in the well bore, which comprises lowering upper and lower well packers on a tubular string in the well casing to the region of the casing opening, anchoring the lower packer in packed-cfrr condition in the casing below the opening against downward movement in the casing and to prevent downward passage of fluid therethrough, elevating the upper packer frorn-the lower packer, anchoring the upper packer in packed-olf condition in the casing above the opening and against upward movement in the casing, applying uid pressure through the tubular string and upper packer to the well casing between the anchored packers tending to urge the lower packer downwardly and the upper packer upwardly, thereafter releasing the upper packer from the casing and lowering it toward the lower packer, then connecting the upper packer to the lower packer, releasing the lower packer from the casing, and moving the upper and lower packers as a unit longitudinally in the well casing.

7. In subsurface apparatus for applying pressure in a well bore: an upper retrievable packer adapted to be lowered in the well bore on a tubular running-in string and to be anchored in the well bore against upward movement therein; a lower retrievable packer adapted to be lowered in the well bore and anchored therein against downward movement and to prevent downward passage of fluid therethrough; and means providing a releasable connection between said upper and lower packers which enables said upper packer to be disconnected from said lower packer while in the well bore and then reconnected to said lower packer while in the well bore.

8. In subsurface apparatus for applying pressure in a well bore: an upper retrievable packer adapted to be lowered in the well bore on a tubular running-in string and to be anchored in the well bore against upward movement therein; a lower retrievable packer adapted to be lowered in the well bore and anchored therein against downward movement and to prevent downward passage of iluid therethrough; and an overshot releasably connecting said upper and lower packers together for movement as a unit in the well bore and for releasing said upper packer from said lower packer while in the well bore.

9. In subsurface apparatus for applying pressure in a well bore: an upper retrievable packer adapted to be lowered in the Well bore on a tubular running-in string and to be anchored in the well bore against upward movement therein; a lower retrievable packer adapted to be lowered in the well bore and anchored therein against downward movement and to prevent downward passage of fluid therethrough; and an overshot secured to said upper packer and adapted to be piloted over and connected to a portion of said lower packer to couple said packers together.

10. In subsurface apparatus adapted to be lowered in a well casing disposed in a well bore: an upper retrievable packer adapted to be lowered on a tubular string in and anchored to the well casing; a lower retrievable packer adapted to be lowered in and anchored to the well casing against downward movement therein and to prevent downward passage of fluid therethrough; and a releasable coupling between said upper and lower packers, said coupling including means movable longitudinally and without rotation in the well casing for disconnecting said upper and lower packers from each other, while in the well casing, and for subsequently reconnecting said packers, while in the well casing, for longitudinal movement as a unit in the well casing.

11. In subsurface apparatus adapted to be lowered in a well casing disposed in a well bore. an upper retrievable packer adapted to be lowered on a tubular string in and anchored. to the well casing; a lower retrievable packer adapted to'be lowered in and anchored to the well casing, against downward movement therein and to prevent downwardV passage of fluid therethrough said lower packer embodying means movable longitudinally with respect to other portions of said lower packer to positions selectively preventing or permitting anchoring of said lower packer in the well casing; and a releasable coupling between said upper packer and said means, said coupling including instrumentalities for disconnecting said upper packer from said means and for reconnecting said upper packer to said means in response to lowering of said upper packer in the well casing, whereby longitudinal movement of said upper-packer in the well casing shifts said means longitudinally relative to other portions of said lower packer to a position preventing anchoring of said lower packer in the well casing and allow said upper and lower packers to be moved as a unit longitudinally in the well casing.

12. In subsurface apparatus adapted to be lowered in a well casing disposed in a well bore: an upper retrievable packer adapted to be lowered on a tubular string in and anchored to the well casing; a lower retrievable packer adapted to be lowered in and anchored to the well casing against downward movement therein and to prevent downward passage of iluid therethrough, said lower packer embodying means movable longitudinally with respect to other portions of said lower packer to positions selectively preventing or permitting anchoring of said lower packer in the well casing; and a releasable overshot connected to said upper packer and movable over said means into coupling engagement with said means, said overshot including instrumentalities for disconnecting said upper packer from said means and for reconnecting said upper packer to said means in response to lowering of said upper packer in the well casing, whereby longitudinal movement of said upper packer in the well casing shifts said means longitudinally relative to other portions of said lower packer to a position preventing anchoring of said lower packer in the well casing to allow said upper and lower packers to be moved as a unit longitudinally in the well casing.

13. In subsurface apparatus adapted to be lowered in a well casing disposed in a well bore: an upper retrievable packer adapted to be lowered on a tubular string in and anchored to the well casing against upward movement therein; a lower retrievable packer adapted to be lowered in and anchored to the well casing against downward movement therein and to prevent downward passage of iluid therethrough; and a releasable coupling between said upper and lower packers, said coupling including means for disconnecting said upper and lower packers from each other and for reconnecting said packers, while in the well casing, for longtiudinal movement as a unit in the well casing.

14. In subsurface apparatus adapted to be lowered in a well casing disposed in a well bore: an upper retrievable packer adapted to be lowered on a tubular string in and-anchored to the well casing against upward movement therein; a lower retrievable packer adapted to be lowered in and anchored to the well casing against downward movement therein and to prevent downward passage of fluid therethrough, said lower packer embodying means movable longitudinally with respect to other portions of said lower packer to positions selectively preventing or permitting anchoring ot said lower packer in the well casing; and a releasable overshot connected to said upper packer and movable over said means into coupling engagement with said means, said overshot including instrumentalities for disconnecting said upper packer from said means and for reconnecting said upper packer to said means in response to lowering of said upper packer in the well casing, whereby longitudinal movement of said 19 upper packer in the well casing shifts said means vlongitudinally relative to other portions of said lower packer to a position preventing anchoring of said lower .packer in the well casing to allow said upper and lower packers to be moved as a unit longitudinally in the well casing.

References Cited in the file of this patent UNITED STATES PATENTS Y Otis July 25, Howard Aug. 18, Morrisett July`5, Botkin Aug. 17, Baker Jan. 30, Denton June 19, 

